When pieces of any relatively hard polyamide, having a defined melting point above about 250 degrees Celsius, are friction welded, small particles, a few hundredths of a millimeter thick and up to several millimeters long that have a chip or hair-like shape (hereafter called "turnings"), are produced at the weld location. The turnings are expelled, or thrown, from the joint weld as solid particles. For containers manufactured from polyamide pieces, a portion of the turnings are depositied inside the container. These turnings can only be removed with difficulty, and at high cost, by methods such as suction or flushing the interior. Further, these cleaning methods may only be used if the container has an open interior, that is, it has no baffles, partition walls, ribs or chambers. If, on the other hand, the inside of the container is not smooth, rather is provided with ribs, baffles, chambers or the like, then the container is, in all likelihood, produced from a number of pieces that must be joined and a large number of turnings will be found within the finished container. The simple, clean interior container can be produced more simply by means of the blow process while the more complex containers require a joining process such as friction welding. If polyamide containers having screens, valves, nozzles, regulators or similar constricted points are used after production, while containing turnings from a friction welded joint, the turnings will migrate to the constricted points thereby reducing the efficiency of, or rendering inoperable, the container. This is readily apparent if the polyamide container is part of a vehicular hydraulic steering or braking system.
It is known to "capture" or "trap" the excess molten material, produced in friction welding, which is dislocated to the side, forming a weld burr, by including recesses in the profile, or design, of the welded joint (for example, "Vibrations-Schweissgeraet Modell 2100 von Branson" prospectus-4/79). Practice, however, shows that this method does not suffice for the joining of polyamide parts since it cannot prevent the turnings being thrown or forced into the inside of the container.